The oxidation of Pd(111) leads to an incommensurate surface oxide, which was studied by the use of scanning tunneling microscopy, surface x-ray diffraction, high resolution core level spectroscopy, and density functional calculations. A combination of these methods reveals a two-dimensional structure having no resemblance to bulk oxides of Pd. Our study also demonstrates how the atomic arrangement of a nontrivial incommensurate surface can be solved by molecular dynamics in a case where experimental techniques alone give no solution.

The oxidation of the Pd(100) surface at oxygen pressures in the ${10}^{-6}$ to ${10}^3\mathrm{m}\mathrm{b}\mathrm{a}\mathrm{r}$ range and temperatures up to 1000 K has been studied in situ by surface x-ray diffraction (SXRD). The results provide direct structural information on the phases present in the surface region and on the kinetics of the oxide formation. Depending on the $(T,p)$ environmental conditions, we observe either a thin $(\sqrt{5}\times \sqrt{5})R27°$ surface oxide or the growth of a rough, poorly ordered bulk oxide film of PdO predominantly with (001) orientation. By either comparison to the surface phase diagram from first-principles atomistic thermodynamics or by explicit time-resolved measurements we identify a strong kinetic hindrance to the bulk oxide formation even at temperatures as high as 675 K.

High resolution measurements are reported of the surface core-level shift of the 3d level for the Rh(111), Rh(110), Pd(111), Pd(110), and Ag(111) single-crystal surfaces. These measurements and earlier ones for the Mo(110), Rh(100), and Pd(100) surfaces are analyzed by ab initio calculations of the surface core-level shift. The calculations are found to reproduce well the trends of the experimental shifts with the 4d metal and with the crystal plane. The comparison between these experimental and theoretical results demonstrates the importance of proper inclusion of final-state effects for accurate calculations of surface core-level shifts. A core hole in a surface atom is found to be better screened than one in a bulk atom for the 4d metals to the left of Pd in the Periodic Table. The use of the Z+1 approximation to describe the core hole is investigated both by explicit use of this approximation and by performing calculations for 1s and 3d core holes, respectively. The Z+1 approximation is found to be well obeyed in the case of Ag whereas for the rest of the 4d transition metals it is less precise, introducing errors of typically 0.1 eV.

The structure of the oxygen-induced $p(4\times 4)$ reconstruction of Ag(111) is determined by a combination of scanning tunneling microscopy, surface x-ray diffraction, core level spectroscopy, and density functional theory. We demonstrate that all previous models of this surface structure are incorrect and propose a new model which is able to explain all our experimental findings but has no resemblance to bulk silver oxide. We also shed some light on the limitations of current density functional theories and the potential role of van der Waals interactions in the stabilization of oxygen-induced surface reconstructions of noble metals.

The atomic and electronic structure of the lattice-mismatched $h\text{−}\mathrm{B}\mathrm{N}∕\mathrm{Pt}\left(111\right)$ and $h\text{−}\mathrm{B}\mathrm{N}∕\mathrm{Rh}\left(111\right)$ interfaces formed by pyrolitic reactions with vaporized borazine has been studied by low-energy electron diffraction, scanning tunneling microscopy, x-ray-absorption spectroscopy, and core-level and valence-band photoemission. It has been found that on Pt(111), $h\text{−}\mathrm{B}\mathrm{N}$ forms a nearly flat monolayer, insignificantly corrugated across the supercell. On Rh(111), $h\text{−}\mathrm{B}\mathrm{N}$ grows in form of a nanomesh, as originally observed by Corso et al. [Science 303, 217 (2004)]. The structural difference between the $h\text{−}\mathrm{B}\mathrm{N}∕\mathrm{Pt}\left(111\right)$ and $h\text{−}\mathrm{B}\mathrm{N}∕\mathrm{Rh}\left(111\right)$ interfaces is associated with the strength of chemical interaction between $h\text{−}\mathrm{B}\mathrm{N}$ and the substrate surface. A stronger orbital hybridization on Rh(111) results in a stronger attraction of the monolayer to the metal surface at favorable adsorption sites resulting in a highly corrugated structure (nanomesh). It has been shown that the electronic structure of the outer (elevated) and inner (attracted to the surface) nanomesh sites is very different as a result of different chemical bonding to the substrate (weak and strong, respectively).